This invention relates generally to the field of dentistry, and in particular to the reduction of teeth to facilitate placement of a dental prosthetic device, such as a crown. Or specifically, the invention is related to a dental tool and methods for measuring the amount of tooth reduction.
Artificial dental crowns are used as a restoration for teeth, and are particularly useful when teeth have been broken, have been weakened by decay, or have one or more large fillings. Dental crowns are constructed to fit over the remaining portion of the tooth to make the tooth stronger and provide the tooth with the shape and contour of the natural tooth. As such, crowns are often referred to as caps.
Dental crowns are typically fabricated outside the patient's mouth and then installed in the mouth. The manner of installation may vary depending on the nature of the crown. For example, full crowns are employed to cover the entire surface of a tooth as well as the sides of the tooth. Partial crowns are inlays which cover the top surface and portions of the sides. Inlays are employed to cover central portions of the top surface and may also extend partially onto the sides. Finally, veneers are used to cover a side surface of a tooth. A detailed discussion of how such dental crowns may be placed onto a tooth is set forth in U.S. Pat. No. 5,525,059, the complete disclosure of which is herein incorporated by reference.
Dental crowns may be employed to treat a variety of conditions. For example, as previously mentioned, the tooth may have been previously weakened by decay or may have a very large filling. Another reason for using a crown is if the individual has discolored fillings and would like to improve the appearance of the tooth. As a further example, the patient may have had an endodontic treatment of the root requiring protection of the remaining tooth.
Dental crowns may be constructed of a variety of materials. For example, the crown may be constructed of a porcelain that is bonded to a precious metal. In such cases, the precious metal is used to form the base and the porcelain is applied in layers over the metal base. As another example, the crown may be constructed entirely of porcelain. Because these look very natural, they may often be used for the front teeth. Other examples include porcelain and composite resin materials, glass, and precious metals, such as gold, platinum and palladium. A further description of materials used for dental crowns and how they may be bonded to the underlying tooth is set forth in U.S. Pat. No. 6,183,256, the complete disclosure of which is herein incorporated by reference.
In order to receive a crown, the dentist must first alter the shape of the tooth to a size and shape most conducive for receiving a crown. To do so, the dentist will typically remove most of the outer surface of the tooth, leaving a strong inner core. Ideally, the amount of tooth removed will be about the same as the thickness of the crown to be fitted. After the tooth has been formed to the proper shape, an impression of the prepared tooth along with the opposing jaw is used to determine the manner in which the teeth are brought together when the patient bites down. The impressions are then used by a dental technician to fabricate the crown to the shape of the reduced tooth.
Determining the appropriate size and shape of the tooth to be fitted with a crown is a difficult process, especially when the tooth is near the back of the patient's mouth. In such cases, it is nearly impossible to determine the amount of tooth that has been removed. However, determination of the amount of reduction is critical in order to ensure that the crown will properly fit. For example, if the tooth is-reduced too much, the crown may not fit properly. On the other hand, if the occlusal surface is not sufficiently reduced, the crown will be too large and will interfere with the patient's bite.
In order to determine the amount of tooth reduction, some have proposed the use of a thin rubber strip upon which the patient is instructed to bite. If the dentist is unable to pull the rubber strip from the patient's mouth, the dentist assumes that the tooth has not been sufficiently reduced in size. However, for teeth near the back of the patient's mouth, it is nearly impossible to appropriately position such a rubber strip in the patient's mouth.
Hence, this invention relates to a tooth reduction measuring tool along with methods for its use to facilitate proper tooth reduction when preparing for a crown.